Bolm Inst. oceanogr., S Paulo, 40(1/2):87-91, 1992

lhe karyotype of Cathorops sp, a marine from Brazil

Vicente GOMES; PHAN Van Ngan & Maria José de Arruda Campos Rocha PASSOS

Instituto Oceanográfico da Universidade de São Paulo (Caixa Postal 9075, 01065-970 São Paulo, SP, Brasil)

• Abstract: Cathorops sp has the diploid number of 54 chromosomes. The karyotype comprises 1m + sm, 6m, 6sm and 14st pairs. This result is compared with those of other species of , mainly Ariopsis fe/is and Arius dussumieri, found in literature.

• Descriptors: Cytogenetic, Chromosomes, Karyotypes, Marine fishes, Arüdae, Calhorops sp, Cananéia, BraziL

• Descritores: Citogenética, Cromossomos, Cari6tipos, Peixes marinhos, Arüdae, Calhorops sp, Cananéia: SP.

For alI other arüd species cited in this work the Introduction nomenclature of Taylor & Menezes (op. cit.) and Figueiredo & Menezes (1978) was employed. Fishes belonging to the family Ariidae (order ln this paper the karyotype of Cathorops sp is described Siluriformes), popularly known as marine , have and compared with those of Ariopsis fe/is and Arius circumtropical occurrence. They can be found in the sea, dussumieri found in the literature. estuaries and river mouths. Although the literature related to these ftshes is extensive their systematics is highly controversial (Wheeier & Baddokwaya, 1981; Higushi, 1982) and needs to be revised. Material and methods Cytogenetical methods have been used as an aid to solve problems related to systematics and evolution of Specimens were colIected in the estuarine region of fishes and other . Chromosome ioformation on Cananéia, São Paulo, Brazil (25"01'S; 47"56'W) from about 129 species belongiog to 13 families of marine and May 1981 to November 1986. The animais were kept alive freshwater catfishes is available (Fitzsimons et a/., 1988). ln in 1000 liters tanks with running sea water until being relation to the family Ariidae, as far as wc know, oniy employed. They were then injected intraperitoneally with five species have been karyotyped, including the one 0,2 m1/100 g body weight of 0,5% colchicine in salioe presented in this paper. solution, sacrificed 4 to 6 hours later and the kidney was The fish employed in this work is often denominated removed for chromosome preparations folIowing the as Cathorops spixii and used to be considered as the oniy procedures described by LeGrande & Fitzsimons (1976) species of the recognized along the Brazilian coast with slight modification as described in Gomes et aI. (Fig. 1). Recent studies (Taylor & Menezes, 1978), (1990). The specimens employed were fixed in formalin however, indicate that more than one species are probably 4% and kept in our laboratory at the Instituto being denominated by this name. ln spite of the fact that Oceanográfico da Universidade de São Paulo. no morphological differences between our specimens were The metaphases were photographed, the chromosomes observed, Dr. Naércio A. Menezes (pers. com.) suggested were counted and the karyograms mounted from to refer to them as Cathorops sp because of the above photographic prints. Estimation of the chromosome size mentioned uncertainty of the of Cathorops in micrometers was ma de by measuring two easily species compleXo identifiable chromosomes of a set in middle metaphase using a micrometric eyepiece placed in microscope Wild M20 and then correlating these measures with all the Contr. no. 734 do Inst. oceanogr. da Usp. chromosomes of the same set in a photographic print. 88 Bolm Inst. oceanogr., S Paulo, 40(1/2),1992

Fig. 1. A speclmen of Cathorops sp used ln thls study. Total length, 174 mm.

The arm ratios (long arm/short arm) were calculated chromosomes of the first pair noticeable in several cells and terminology for centromeric position followed the examined due to the size of the short arms. Variations criteria of Levan et ai. (1964). To facilitate the comparisons between chromosomes of a same pair were also observed between our data with other data found in the literature the in other fish species as Lepomis cyanellus (Roberts, 1964) chromosome types were gathered in groups following andHoplias malabaricus (Bertollo, 1978), for example. ln Uyeno et ai. (1983). Arm numbers (AN) were calculated Cathorops sp the difference between these two considering m (metacentric) and sm (submetacentric) chromosomes of the frrst pair is more striking at earIy chromosomes as biarmed and st (subtelocentric) as metaphases, when the chromosomes are still not uniarmed. compIeteIy contracted. There are several possibilities that could explain this phenomenon, such as pericentric inversion, heterogeneity in the chromatin condensation during mitosis, etc. It could also be due to an erior resulting Results from misinterpretation during pairing, but, the distinctness between these two chromosomes and the other Good mitotic metaphase spreads were obtained from 25 chromosomes of m and sm types of the compIement specimens of Cathorops sp, 9 males and 16 females, ranging renders this possibility remote. The possibility that tbis from 150 mm to 234 mm in totallength. difference is due to sexual dimorpbism can be ruled out A total of 257 spreads was examined, 103 for the males since it occurs in both males and females. Artifacts during and 154 for the females. The cells with dipIoid number of preparations, although not totally discarded, are also 2n = 54 chromosomes account for 'ir7.38% of the total improbable due to the frequency of the heteromorpbism countings for the males and 83.12% for the females. The observed. At the moment, the origin and significance of the chromosome total Iength in micrometers taken as an variability in the tirst chromosome pair of Cathorops sp average from 10 selected spreads ranged from 6.29 Ilm to karyotype remain to be elucidated. DoubteIess, the use of 1.81.um. some banding methods will be very useful in clarifying tbis The two chromosomes of the first pair presented short problem. arms of different sizes detectabIe in about 60% of the cells LeGrande (1981), studying the karyologica1 evoIution of examined. With this heteromorpbism it was possibIe to Siluriform tishes, suggested that the probable ancestral classify each of them inta a distinct type. So, the karyotype karyotype of the whole order would be of 2n = 56± 2; with consisted of 1 m + sm pair, 6 m pairs, 6 sm pairs and 14 st. bigh AN, i.e., a bigh proportion ofbiarmed eIements; with pairs (Fig. 2). No heteromorpbism between males and the chromosomes gradually decreasing in size and with the females was observed. biggest chromosome of about 5.0% of the total size of the complemento Tbis hypothesis has been reinforced by a series of data. For instance, the medium number of chromosomes in the family Bagridae, considered a Discussion primitive group within the order, is also of 2n = 56±2 (Sharma & Tripatbi, 1986). The tive species of Arüdae As described above, the karyotype of Cathorops sp karyotyped until now, induding the one here studied, showed a slight morphological difference between the two GOMES et ai.: Karyotype: Calhorops sp: Brazil 89

..

1 2 3 4 5 6 7

8 9 10 11 12 13 14

15 17 16 18 19 20 21 , .. 22 23 24 25 26 27

10 pm

Fig. 2. Karyotype of a male Cathorops sp. follow the same trend (Table 1). This family is also have contributed to the karyological evolution of this considered as a group with primitive characteristics species. among Siluriformes (Gosline, 1975). Among the Besides these trends in karyological evolution, it is karyotyped arüds, four species: Ariopsis felis (LeGrande, noticeable that the Siluriformes undergone extensive 1980),Arius dussumieri (Rishi et ai., 1983), Bagre marinus alterations in chromosome morphology during evolution (Fitzsimons et ai., 1988), Cathorops sp (present study) have probably due to the high speciation of the order 2n=54, and one, Bagre bagre (Gomes et ai., 1990), has (LeGrande et ai., 1984). Karyotypes can be very distinct 2n = 56. even among close related species as is the case of the arüds The relative size of the biggest chromosome pair of Bagre bagre and B. marinus (Gomes et ai., 1990). Cathorops sp is on average 6.68% of total size of the Nevertheless, when one compares the karyotypes of complement, being larger than that expected for the Cathorops sp and Ariopsis felis some remarkable possible ancestral karyotype. This fact suggests that similarities can be noticed. Both have the same number of mechanisms which result in changes of chromosome size chromosome arms (AN = 80) and if m and sm (such as fusions, translocations, duplications, etc.) could chromosomes of Cathorops sp are grouped together as did

Table 1. Karyotypes of some arlid catflshes. ln parentheses, chromosome types of Cathorops sp grouped together. m, metacentric; msm, meta-submetacentrlc; sm, submetacentrlc; st, subtelocentrlc; stt, subtelo-telocentric

Species 2n AN m msm sm st stt Reference

Bagre marinus 54 74 12 8 34 Fitzsimons et ai. (1988)

Bagre bagre 56 106 24 26 6 Gomes et ai. (1990)

Arius dussumieri 54 84 12 18 24 Rishi et ai. (1983)

Ariopsis felis 54 80 26 28 LeGrande (1980)

Cathorops sp 54 80 13 (26) 13 28 (28) present study 90 Bolm Inst. oceanogr., S Paulo, 40(1/2), 1992

LeGrande (1980) for A. telis, both species show the same Acknowledgments number of msm and stt chromosome types (Table 1). Other similarities between these two species can be verified by We wish to express our gratitude to Dr. Naércio Aquino comparing the karyotypes presented by LeGrande (1980) Menezes, Museum of Zoology, São Paulo University, and for A. telis and by this study for Cathorops sp (Fig. 2). For to Dr. Luiz Antonio Carlos Bertollo, Biologica1 Sciences instance, the chromosomes of both species decrease Department, Federal University of São Carlos for reading gradually in size and all have identifiable second arms the manuscript and for the valuable suggestions. This work ranging from large to small. ln A. teUs the larger msm was supported by grant from "Fundação de Amparo à chromosome pair tended to be submetacentric. ln Pesquisa do Estado de São Paulo - FAPESP" (81/1821-5) Cathorops sp the larger pair of msm group is often at the and "Conselho Nacional de Desenvolvimento CientíficO e limit between m and sm types. The smaller msm Tecnológico - CNPq" (104243-83; 300299m). chromosomes of both A. telis and Cathorops sp were metacentric.

Arius dussumieri has the same chromosome number References (2n = 54) and also similar arm number (AN = 84) as Cathorops sp andA. te/is (AN=8O) with a relatively higher number of biarmed elements (Rishi et ai., 1983) BERTOLLO, L. A. C. 1978. Estudos citogenéticos (Table 1). no gênero Hoplias Gill, 1903 (Pisces-Erythrinidae). Tese de doutorado. Universidade de São Paulo, The real meaning of these karyological similarities Faculdade de Medicina de Ribeirão Preto. 164p. + between the three ariid species belonging to three different tabs + 6gs. genera is difticult to ascertain at the momento Since many authors agree that the systematics of Arüdae group should FIGUEIREDO, J. L. & MENEZES, N. A. 1978. be reviewed (Taylor & Menezes, 1978; Higushi,1982) we Teleostei I. Manual de peixes marinhos do sudeste believe that citogenetical data could be of great value to the do Brasil. ll. São Paulo, Museu de Zoologia da solution of the problem. The systematic positions of the Universidade de São Paulo. UOp. species of the family, however, could only be established after a detailed phylogenetical study using as many FITZSIMONS, J. M.; LEGRANDE, W. H. & characters as necessary. KORTH, J. W. 1988. Karyology of the marine cat6sh Bagre marinus (Ariidae) with an analysis of chromosome numbers among siluriform fishes. J apan. J. Ichthyol., 35(2):189-193.

GOMES, V.; PHAN, V. N. & PASSOS, M. J. A. C. Conclusion R. 1990. Karyotype of a marine cat6sh, Bagre bagre, from Brazil. Japan. J. Ichthyol., The karyotype of Cathorops sp comprises 1 m + sm, 6 37(3):321-323. m, 6 sm and 14 st pairs of chromosomes. The diploid and arm number are 2n=54 and AN =80 respectively. These GOSLINE, W. A. 1975. The palatine-maxillary features are similar to those of Ariopsis telis and Arius mechanism in catfishes, with comments on the dussumieri described in the literature. The meaning of evolution and zoogeography of modem siluroids. those similarities is dif6cult to ascertain at the momento Occ. Papo Calif. Acad. Sci.,(12O):1-31. More citogenetical data could be useful for the systematic of the members of Arüdae family. HIGUSHI, H. 1982. Estudo osteológico de bagres marinhos do litoral sul do Brasil (Osteichthyes; Silurioide~ Ariidae). Dissertação de mestrado. Universidade de São Paulo, Instituto de Biociências. 135p. + tabs + figs. Resumo LEGRANDE, W. H. 1980. The chromosome Foram realizados estudos cromossômicos em 25 complement of Ariopsis feUs (Siluriformes, espécimens de Cathorops sp pelo método de air-drying. Arüdae). Japan. J. Ichthyol., 27(1):82-84. O número modal diplóide encontrado foi de 54 cromossomos sendo 1 par m + sm, 6 pares m, 6 pares _--:-______1981. Chromosomal evolution sm e 14 pares st. Os resultados são comparados com in North American catfishes (Siluriformes: dados da literatura referentes a cromossomos de outros Ictaluridae) with particular emphasis of the ariídeos, principalmente de Ariopsis telis e Arius madtoms Noturus. Copeia, (1):33-52. dussumieri . GOMES et al.: Karyotype: Cathorops sp: Brazil 91

LEGRANDE, W. H.; DUNHAM, R.A. & SHARMA, O.P. & TRIPATHI, N.K. 1986. Karyotypic SMITHERMAN, R.D. 1984. Karyology of three diversity in the genus Mystus (Bagridae, Pisces). species of catfishes (Ictaluridae: Ictalunls) and hybrid Cytologia, 51(1):1-9. COmbinatiODS. Copeia, (4):873-878. TAYLOR, W. R. & MENEZES, N. A. 1978. Arüdae.ln _--:---:-_---:-: & F1TZSIMONS, J.M.1976. Karyology FISCher, W., cd. FAO spccies idcntification sheets for of the mullcts Mugil curema and M. cephalus fishery purposes. Westem Central Atlantic (fishing (percifonnes: Mugilidae) from Louisiana. Copeia, area 31). Rome, FAO. v.1. (2):388-391. UYENO, T.; MIlLER, R. R. & FITZSIMONS, J. M. LEVAN, A.; FREDGA, K. & SANDBERG, A.A.1964. 1983. Karyology of the cyprinodontoid tishes of Nomenclaturc for ccntromeric position on the Mexican family Goodeidae. Copeia, chromosomes. Hereditas, 52:201-220. (2):497-510.

RISIn, K.K.; SINGH, J. & HAOBAM, M.S. 1983. WHEELER, A. & BADDOKWAYA, A. 1981. The Karyological study on a marine catfish, Arius generic nomenclature of the marine catfishes usua1ly dussumieri (Val.) (Ariidae: Siluriformcs). Chrom. referred to the genus Arius (Osteichthyes - Inf. Serv., (34):7-9. Silurlfonnes). J. nato Hist., 15(5):769-773.

ROBERTS, .F. L. 1964. A chromosome study oftwcnty spccies of Centrarchidae. J. Morphology, (Manuscript received 16 June 1992; Mlised 23 115:401-418. November 1992; QCcepted 10 December 1992)